Evaluation of mirrored muscle activity in patients with Complex Regional Pain Syndrome

Objective

Motor dysfunction in Complex Regional Pain Syndrome (CRPS) has been associated with bilateral changes in central motor processing, suggesting abnormal coupling between the affected and unaffected limb. We evaluated the occurrence of involuntary muscle activity in a limb during voluntary movements of the contralateral limb (i.e., mirror activity) in unilaterally affected patients to examine disinhibition of contralateral motor activity in CRPS.

Methods

Mirror activity was examined during unimanual rhythmic flexion–extension movements of the wrist through in-depth analysis of electromyography recordings from the passive arm in 20 CRPS patients and 40 controls.

Results

The number of mirror-epochs was comparable for both arms in both CRPS patients and controls. Mirror-epochs in the affected arm of patients were comparable to those in controls. Mirror-epochs in the unaffected arm were shorter and showed less resemblance (in terms of rhythm and timing) to activity of the homologous muscle in the moving arm compared to mirror-epochs in controls.

Conclusions

No evidence for disinhibition of contralateral motor activity was found during unimanual movement.

Significance

Although motor dysfunction in CRPS has been associated with bilateral changes in cortical motor processing, the present findings argue against disinhibition of interhemispheric projections to homologous muscles in the contralateral limb during unimanual movement.     

Corticomotor excitability of arm muscles modulates according to static position and orientation of the upper limb

Objective

We investigated how multi-joint changes in static upper limb posture impact the corticomotor excitability of the posterior deltoid (PD) and biceps brachii (BIC), and evaluated whether postural variations in excitability related directly to changes in target muscle length.

Methods

The amplitude of individual motor evoked potentials (MEPs) was evaluated in each of thirteen different static postures. Four functional postures were investigated that varied in shoulder and elbow angle, while the forearm was positioned in each of three orientations. Posture-related changes in muscle lengths were assessed using a biomechanical arm model. Additionally, M-waves were evoked in the BIC in each of three forearm orientations to assess the impact of posture on recorded signal characteristics.

Results

BIC-MEP amplitudes were altered by shoulder and elbow posture, and demonstrated robust changes according to forearm orientation. Observed changes in BIC-MEP amplitudes exceeded those of the M-waves. PD-MEP amplitudes changed predominantly with shoulder posture, but were not completely independent of influence from forearm orientation.

Conclusions

Results provide evidence that overall corticomotor excitability can be modulated according to multi-joint upper limb posture.

Significance

The ability to alter motor pathway excitability using static limb posture suggests the importance of posture selection during rehabilitation aimed at retraining individual muscle recruitment and/or overall coordination patterns.     

Complex regional pain syndrome,alexithymia, and psychological distress

Objective

This study aims to elucidate the relationships between alexithymia, psychological distress, and pain in persons with complex regional pain syndrome (CRPS).

Methods

Participants were 60 Israeli adults ages 19–65. This is a cross sectional study with a comparison group. Alexithymia, psychological distress, and pain were assessed in 30 individuals with CRPS in comparison to 30 gender- and age-matched persons with lower back pain (LBP). Assessments included the Toronto Alexithymia Scale, Hospital Anxiety and Depression Scale, and two subscales of the McGill Pain Questionnaire.

Results

Persons with CRPS had significantly higher ratings of psychological distress and of alexithymia when compared to LBP controls. Pain severity was significantly associated with higher levels of alexithymia and psychological distress among persons with CRPS, but not among controls. Alexithymia and pain severity correlations were significantly different between the two groups. In persons with CRPS, the relationships between alexithymia and pain severity and between difficulty identifying feelings and pain were not confounded by psychological distress.

Conclusions

To our knowledge, this is the first cross sectional study providing empirical evidence on the relationship between alexithymia and CRPS. From the perspective of conceptualizing alexithymia as an outcome of CRPS, findings highlight the importance of early CRPS diagnosis and support the provision of care that addresses pain-related psychological distress and alexithymia among CRPS patients. Also, findings underscore the need to generate alternative, non-physical avenues, such as learning to identify feelings for processing pain, in order to reduce pain among persons with CRPS.     

Efferent and afferent evoked potentials in patients with adrenomyeloneuropathy

Objective

This paper investigates efferent and afferent conductions of the central nervous system by various evoked potentials in patients with adrenomyeloneuropathy (AMN).

Patients and methods

Ten pure AMN patients without cerebral involvement were studied. Motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs), auditory brainstem response (ABR), and pattern reversal full-field visual evoked potentials (VEPs) were recorded. For MEP recording, single-pulse or double-pulse magnetic brainstem stimulation (BST) was also performed.

Results

Abnormal MEP was observed in all ten patients, abnormal SEP in all ten, abnormal ABR in nine, and abnormal VEP in only one. Brainstem latency was measured in three of the seven patients with central motor conduction time (CMCT) prolongation. The cortical–brainstem conduction time was severely prolonged along the normal or mildly delayed brainstem–cervical conduction time in those three patients.

Conclusions

The pattern of normal VEP and abnormal MEP, SEP, ABR is a clinically useful electrophysiological feature for the diagnosis. BST techniques are helpful to detect, functionally, intracranial corticospinal tract involvement, probably demyelination, in pure AMN patients.     

Effect of afferent input on motor cortex excitability during stroke recovery

Objective

Afferent input is proposed to mediate its effect on motor functions by modulating the excitability of the motor cortex. We aimed to clarify – in a longitudinal study – how afferent input affects motor cortex excitability after stroke and how it is associated with recovery of hand function.

Methods

The motor cortex excitability was studied by measuring the reactivity of the motor cortex beta rhythm to somatosensory stimulation. We recorded the amplitude of the suppression and subsequent rebound of the beta oscillations during tactile finger stimulation with MEG in 23 first-ever stroke patients within one week and at 1 and 3 months after stroke, with concomitant evaluation of hand function.

Results

The strength of the beta rhythm rebound, suggested to reflect decreased motor cortex excitability, was weak in the affected hemisphere after stroke and it was subsequently increased during recovery. The rebound strength correlated with hand function tests in all recordings.

Conclusion

Motor cortex excitability is modulated by afferent input after stroke. The motor cortex excitability is increased in the AH acutely after stroke and decreases in parallel with recovery of hand function.

Significance

The results implicate the importance of parallel recovery of both sensory and motor systems in functional recovery after stroke.     

EEG-based classification of imaginary left and right foot movements using beta rebound

Objective

The purpose of this study was to investigate cortical lateralization of event-related (de)synchronization during left and right foot motor imagery tasks and to determine classification accuracy of the two imaginary movements in a brain–computer interface (BCI) paradigm.

Methods

We recorded 31-channel scalp electroencephalograms (EEGs) from nine healthy subjects during brisk imagery tasks of left and right foot movements. EEG was analyzed with time–frequency maps and topographies, and the accuracy rate of classification between left and right foot movements was calculated.

Results

Beta rebound at the end of imagination (increase of EEG beta rhythm amplitude) was identified from the two EEGs derived from the right-shift and left-shift bipolar pairs at the vertex. This process enabled discrimination between right or left foot imagery at a high accuracy rate (maximum 81.6% in single trial analysis).

Conclusion

These data suggest that foot motor imagery has potential to elicit left–right differences in EEG, while BCI using the unilateral foot imagery can achieve high classification accuracy, similar to ordinary BCI, based on hand motor imagery.

Significance

By combining conventional discrimination techniques, the left–right discrimination of unilateral foot motor imagery provides a novel BCI system that could control a foot neuroprosthesis or a robotic foot.     

Quantitative studies of lower motor neuron degeneration in amyotrophic lateral sclerosis: Evidence for exponential decay of motor unit numbers and greatest rate of loss at the site of onset

Objective

To use our Bayesian method of motor unit number estimation (MUNE) to evaluate lower motor neuron degeneration in ALS.

Methods

In subjects with ALS we performed serial MUNE studies. We examined the repeatability of the test and then determined whether the loss of MUs was fitted by an exponential or Weibull distribution.

Results

The decline in motor unit (MU) numbers was well-fitted by an exponential decay curve. We calculated the half life of MUs in the abductor digiti minimi (ADM), abductor pollicis brevis (APB) and/or extensor digitorum brevis (EDB) muscles. The mean half life of the MUs of ADM muscle was greater than those of the APB or EDB muscles. The half-life of MUs was less in the ADM muscle of subjects with upper limb than in those with lower limb onset.

Conclusions

The rate of loss of lower motor neurons in ALS is exponential, the motor units of the APB decay more quickly than those of the ADM muscle and the rate of loss of motor units is greater at the site of onset of disease.

Significance

This shows that the Bayesian MUNE method is useful in following the course and exploring the clinical features of ALS.     

Which nerve conduction parameters can predict spontaneous electromyographic activity in carpal tunnel syndrome?

Objective

We investigate electrodiagnostic markers to determine which parameters are the best predictors of spontaneous electromyographic (EMG) activity in carpal tunnel syndrome (CTS).

Methods

We enrolled 229 patients with clinically proven and nerve conduction study (NCS)-proven CTS, as well as 100 normal control subjects. All subjects were evaluated using electrodiagnostic techniques, including median distal sensory latencies (DSLs), sensory nerve action potentials (SNAPs), distal motor latencies (DMLs), compound muscle action potentials (CMAPs), forearm median nerve conduction velocities (FMCVs) and wrist–palm motor conduction velocities (W–P MCVs). All CTS patients underwent EMG examination of the abductor pollicis brevis (APB) muscle, and the presence or absence of spontaneous EMG activities was recorded. Normal limits were determined by calculating the means ± 2 standard deviations from the control data. Associations between parameters from the NCS and EMG findings were investigated.

Results

In patients with clinically diagnosed CTS, abnormal median CMAP amplitudes were the best predictors of spontaneous activity during EMG examination (p < 0.001; OR 36.58; 95% CI 15.85–84.43). If the median CMAP amplitude was ?2.1 mV, the rate of occurrence of spontaneous EMG activity was >95% (positive predictive rate >95%). If the median CMAP amplitude was higher than the normal limit (>4.9 mV), the rate of no spontaneous EMG activity was >94% (negative predictive rate >94%). An abnormal SNAP amplitude was the second best predictor of spontaneous EMG activity (p < 0.001; OR 4.13; 95% CI 2.16–7.90), and an abnormal FMCV was the third best predictor (p = 0.01; OR 2.10; 95% CI 1.20–3.67). No other nerve conduction parameters had significant power to predict spontaneous activity upon EMG examination.

Conclusions

The CMAP amplitudes of the APB are the most powerful predictors of the occurrence of spontaneous EMG activity. Low CMAP amplitudes are strongly associated with spontaneous activity, whereas high CMAP amplitude are less associated with spontaneous activity, implying that needle EMG examination should be recommended for the detection of spontaneous activity in those CTS patients whose NCS reveals CMAP amplitudes between 2.1 mV and the lower normal limit (4.9 mV in the present study).

Significance

Using NCS, electromyographers can predict the presence of spontaneous EMG activity in CTS patients.     

Muscle and nerve biopsies: Techniques for the neurologist and neurosurgeon

Objective

Muscle and nerve biopsies are commonly performed procedures for the diagnosis of neuromuscular disorders. Neurologists and neurosurgeons are often consulted to perform these procedures in clinical practice. We provide guidelines in the performance of muscle and nerve biopsies.

Methods

We describe the technique for performance of muscle and nerve biopsy, and review the relevant literature.

Results

The quadriceps muscle is the most typical biopsy site for most myopathies, whereas the sural nerve is the most common nerve biopsy site for most peripheral neuropathies. Other sites may be utilized depending upon the pattern of symptoms or the differential diagnosis. Motor nerves may be sampled in the setting of motor neuron disease, for example. We advocate the use of conduit repair to allow for sensory or motor recovery to occur following nerve biopsy.

Conclusion

The muscle biopsy and nerve biopsy may be performed with high yield, low morbidity, and rare complications.     

Neuromuscular constraints on muscle coordination during overground walking in persons with chronic incomplete spinal cord injury

Objective

Incomplete spinal cord injury (iSCI) disrupts motor control and limits the ability to coordinate muscles for overground walking. Inappropriate muscle activity has been proposed as a source of clinically observed walking deficits after iSCI. We hypothesized that persons with iSCI exhibit lower locomotor complexity compared to able-body (AB) controls as reflected by fewer motor modules, as well as, altered module composition and activation.

Methods

Eight persons with iSCI and eight age-matched AB controls walked overground at prescribed cadences. Electromyograms of fourteen single leg muscles were recorded. Non-negative matrix factorization was used to identify the composition and activation of motor modules, which represent groups of consistently co-activated muscles that accounted for 90% of variability in muscle activity.

Results

Motor module number, composition, and activation were significantly altered in persons with iSCI as compared to AB controls during overground walking at self-selected cadences. However, there was no significant difference in module number between persons with iSCI and AB controls when cadence and assistive device were matched.

Conclusions

Muscle coordination during overground walking is impaired after chronic iSCI.

Significance

Our results are indicative of neuromuscular constraints on muscle coordination after iSCI. Altered muscle coordination contributes to person-specific gait deficits during overground walking.     

Modulation of motor cortex excitability by paired peripheral and transcranial magnetic stimulation

Objective

Repetitive application of peripheral electrical stimuli paired with transcranial magnetic stimulation (rTMS) of M1 cortex at low frequency, known as paired associative stimulation (PAS), is an effective method to induce motor cortex plasticity in humans. Here we investigated the effects of repetitive peripheral magnetic stimulation (rPMS) combined with low frequency rTMS (‘magnetic-PAS’) on intracortical and corticospinal excitability and whether those changes were widespread or circumscribed to the cortical area controlling the stimulated muscle.

Electroconvulsive therapy-induced Wolff–Parkinson–White syndrome: a case report

Objective

Wolff–Parkinson–White (WPW) syndrome is characterized by premature ventricular excitation due to the presence of an abnormal accessory pathway. Electrocardiography (ECG) of patients with WPW syndrome portrays a short PR interval and a wide QRS interval with a delta wave.

Methods

Herein, we report the case of a patient with schizophrenia who developed a wide QRS interval with a delta wave immediately following electroconvulsive therapy (ECT).

Results

Initially, the delta wave disappeared within 2 days after ECT. However, the duration of the delta wave increased exponentially to 4 months when ECT was repeated.

Conclusion

Although the patient's cardiocirculatory dynamics remained normal, we continued to monitor her ECG until the delta wave disappeared because WPW syndrome can lead to serious arrhythmia.     

The effects of electromyography-controlled functional electrical stimulation on upper extremity function and cortical perfusion in stroke patients

Objective

The relation was investigated between hemiparetic arm function improvement and brain cortical perfusion (BCP) change during voluntary muscle contraction (VOL), EMG-controlled FES (EMG-FES) and simple electrical muscle stimulation (ES) before and after EMG-FES therapy in chronic stroke patients.

Methods

Sixteen chronic stroke patients with moderate residual hemiparesis underwent 5 months of task-orientated EMG-FES therapy of the paretic arm once or twice a week. Before and after treatment, arm function was clinically evaluated and BCP during VOL, ES and EMG-FES were assessed using multi-channel near-infrared spectroscopy.

Results

BCP in the ipsilesional sensory-motor cortex (SMC) was greater during EMG-FES than during VOL or ES; therefore, EMG-FES caused a shift in the dominant BCP from the contralesional to ipsilesional SMC. After EMG-FES therapy, arm function improved in most patients, with some individual variability, and there was significant improvement in Fugl–Meyer (FM) score and maximal grip strength (GS). Clinical improvement was accompanied by an increase in ipsilesional SMC activation during VOL and EMG-FES condition.

Conclusion

The EMG-FES may have more influence on ipsilesional BCP than VOL or ES alone.

Significance

The sensory motor integration during EMG-FES therapy might facilitate BCP of the ipsilesional SMC and result in functional improvement of hemiparetic upper extremity.     

Promoting use-dependent plasticity with externally-paced training

Objective

To evaluate use-dependent plasticity (UDP) before and after training under metronome-paced and self-paced conditions.

Methods

Twelve healthy adults were recruited to this cross-over, pseudo-randomized, repeated measures study. Participants performed wrist extension training that was either self-paced, or externally-paced to an auditory metronome at their preferred movement frequency or at a more demanding frequency. Motor evoked potentials from transcranial magnetic stimulation of left primary motor cortex were recorded in right extensor carpi radialis (ECR) and flexor carpi radialis (FCR) to assess corticomotor excitability. The direction and velocity of TMS-evoked wrist movement (stimulus-evoked velocity, SEV) were measured before and after training to evaluate UDP.

Results

The most persistent UDP occurred when training was metronome-paced at the participant’s preferred movement frequency. This training protocol produced spatially selective modulation of resting ECR and FCR corticomotor excitability and directional tuning of TMS-evoked wrist movement toward the trained direction. Metronome-paced training at a more demanding frequency resulted in nonspecific facilitation of resting corticomotor excitability, and did not alter TMS-evoked wrist movement.

Conclusions

These novel findings indicate that externally-paced training at the individual’s preferred frequency facilitates UDP.

Significance

UDP underpins motor recovery after stroke. Externally-paced training may be a useful adjunct to movement rehabilitation therapy.     

Análisis del movimiento de la extremidad superior hemiparética en pacientes con accidente cerebrovascular: estudio piloto

Introduction

As a result of neurophysiological injury, stroke patients have mobility limitations, mainly on the side of the body contralateral to the lesioned hemisphere. The purpose of this study is to quantify motor compensation strategies in stroke patients during the activity of drinking water from a glass.

Material and methods

Four male patient with cerebrovascular disease and four right-handed, healthy male control subjects. The motion analysis was conducted using the Vicon Motion System^® and surface electromyography equipment ZeroWire Aurion^®. We analysed elbow, shoulder and trunk joint movements and performed a qualitative analysis of the sequence of muscle activation.

Results

Trunk, shoulder and elbow movements measured in the stroke patient along the sagittal plane decreased during the drinking from a glass activity, while the movements in the shoulder in the coronal plane and trunk increased. As for the sequence of muscle activation, anterior, middle and posterior deltoid all contracted in the patient group during the task, while the upper trapezius activation remained throughout the activity.

Conclusions

Quantitative analysis of movement provides quantitative information on compensation strategies used by stroke patients, and is therefore, clinically relevant.     

Transcranial magnetic stimulation and PAS-induced cortical neuroplasticity in the awake rhesus monkey

Objective

Externally induced neuroplasticity may be of therapeutic value in several neuro-psychiatric disorders. To facilitate research on mechanisms and to make possible the design of prospective, advanced stimulation protocols without exposing human subjects to risk, we have developed a primate model which allows us to assess changes of motor cortical excitability using transcranial magnetic stimulation (TMS).

Methods

TMS hand muscle representation and cortical excitability were determined in two awake trained rhesus monkeys. Neuroplastic changes of cortical excitability were established by 13 min of paired associative stimulation (PAS) with interstimulus intervals of either 15 or 5 ms.

Results

The representational areas of FDI and APB muscles (3.02–4.96 cm²) were located between the spur of the arcuate and the superior precentral sulcus, indicating the potential to carry out spatially selective cortical stimulation. PAS with an interstimulus interval of 15 ms strongly increased cortical excitability for up to two hours, while 5 ms interval had no effect.

Conclusions

This first systematic TMS and PAS primate study demonstrates that the trained rhesus monkeys represent an exceptional animal model that allows cortical TMS mapping as well as non–invasive assessment and induction of cortical neuroplasticity.

Significance

This animal model offers additional advantageous options not possible with humans, namely an alternative to invasive, morphological or molecular analyses, making it highly suitable for preclinical development of advanced neuroplasticity paradigms without exposing human subjects to risk.     

Early electro-clinical features may contribute to diagnosis of the anti-NMDA receptor encephalitis in children

Objective

To describe initial and follow-up electroencephalographic (EEG) characteristics in anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis.

Methods

Consecutive polygraphic video-EEG recordings were analyzed in nine pediatric patients with anti-NMDAR encephalitis at the initial stage of the disease and during the intermediate period until motor recovery. EEG characteristics in waking and sleep stages as well as EEG correlates of abnormal movements are described.

Results

In six of nine patients with anti-NMDAR encephalitis, the waking EEG showed preserved background activity and either focal or unilateral hemispheric slowing. During non-rapid eye movement (NREM) sleep, a decrease in the expected slow waves and unilateral or diffuse theta-alpha band rhythms were also observed in six of nine children. They all had more favorable outcome than the three children with diffuse slowing. Clinically, unilateral abnormal movements contra-lateral to hemispheric or focal slowing were also indicative of milder severity when compared to generalized abnormal movements and diffuse slowing.

Conclusions

In pediatric patients presenting behavioral disorders and abnormal movements, early EEG patterns may be suggestive of anti-NMDAR encephalitis. Moreover early electro-clinical presentation contributes to outcome prediction.

Significance

This case series demonstrates that early EEG patterns may be suggestive of anti-NMDAR encephalitis in pediatric patients with behavioral disorders and abnormal movements.     

Cortico-conus motor conduction time (CCCT) for leg muscles

Objective

To measure the conduction time from the motor cortex to the conus medullaris (cortico-conus motor conduction time, CCCT) for leg muscles using magnetic stimulation.

Methods

Motor evoked potentials (MEPs) were recorded from tibialis anterior muscles in 51 healthy volunteers. To activate spinal nerves at the most proximal cauda equina level or at the conus medullaris level, magnetic stimulation was performed using a MATS coil. Transcranial magnetic stimulation of the motor cortex was also conducted to measure the cortical latency for the target muscle. To obtain the CCCT, the latency of MEPs to conus stimulation (conus latency) was subtracted from the cortical latency.

Results

MATS coil stimulation evoked reproducible MEPs in all subjects, yielding CCCT data for all studied tibialis anterior muscles.

Conclusions

MATS coil stimulation provides CCCT data for healthy subjects.

Significance

This novel method is useful for evaluation of corticospinal tract function for leg muscles because no peripheral component affects the CCCT.     

The relationship between Bayesian motor unit number estimation and histological measurements of motor neurons in wild-type and SOD1(G93A) mice

Objective

To assess the relationship between Bayesian MUNE and histological motor neuron counts in wild-type mice and in an animal model of ALS.

Methods

We performed Bayesian MUNE paired with histological counts of motor neurons in the lumbar spinal cord of wild-type mice and transgenic SOD1^G93A mice that show progressive weakness over time. We evaluated the number of acetylcholine endplates that were innervated by a presynaptic nerve.

Results

In wild-type mice, the motor unit number in the gastrocnemius muscle estimated by Bayesian MUNE was approximately half the number of motor neurons in the region of the spinal cord that contains the cell bodies of the motor neurons supplying the hindlimb crural flexor muscles. In SOD1^G93A mice, motor neuron numbers declined over time. This was associated with motor endplate denervation at the end-stage of disease.

Conclusion

The number of motor neurons in the spinal cord of wild-type mice is proportional to the number of motor units estimated by Bayesian MUNE. In SOD1^G93A mice, there is a lower number of estimated motor units compared to the number of spinal cord motor neurons at the end-stage of disease, and this is associated with disruption of the neuromuscular junction.

Significance

Our finding that the Bayesian MUNE method gives estimates of motor unit numbers that are proportional to the numbers of motor neurons in the spinal cord supports the clinical use of Bayesian MUNE in monitoring motor unit loss in ALS patients.